One way of discovering what a proposition deals with is to ask ourselves what words we must understand⁠—in other words, what objects we must be acquainted with⁠—in order to see what the proposition means. As soon as we see what the proposition means, even if we do not yet know whether it is true or false, it is evident that we must have acquaintance with whatever is really dealt with by the proposition. By applying this test, it appears that many propositions which might seem to be concerned with particulars are really concerned only with universals. In the special case of “two and two are four,” even when we interpret it as meaning “any collection formed of two twos is a collection of four,” it is plain that we can understand the proposition, i.e. we can see what it is that it asserts, as soon as we know what is meant by “collection” and “two” and “four.” It is quite unnecessary to know all the couples in the world: if it were necessary, obviously we could never understand the proposition, since the couples are infinitely numerous and therefore cannot all be known to us. Thus although our general statement implies